This application claims the benefit of U.S. Provisional Application No. 60/015,342, filed Apr. 19, 1996 and is the National Stage of International Application No. PCT/US97/06639, filed Apr. 18, 1997.
In the commercial production of glass containers by use of an I.S. machine, it is common to employ what is known in the industry as the "blow-and-blow" process for sequentially forming glass containers. A vertically-oriented plunger mechanism is used in combination with a blank mold to achieve initial shaping of a glass parison. The parison is a deformable gob of molten glass which is dropped, vertically downward, into the cavity of the blank mold whereupon pressurized air is applied downward onto the parison to cause it to conformably fill the lower portion of the blank mold cavity. The foregoing step in shaping the parison is commonly referred to as the "settle blow".
At the lower end of the blank mold is a neck ring for shaping what will become the container lip end or neck. Immediately following the aforementioned settle blow, an upwardly directed pressurized air flow or "counter blow" is directed through the neck ring to cause the parison to fill out the blank mold cavity and assume the general shape of a glass container.
During the initial downward insertion of the parison into the blank mold, a funnel is normally disposed at the upper end of the blank mold to facilitate entry of the parison into the mold, after which the funnel is replaced by a baffle to close off the upper end of the blank mold except for air channels through the baffle which direct the downward pressurized air flow during the settle blow step. The baffle remains in place during the upward counter blow, and the counter blow results in the full shaping of the parison. Following the counter blow step of the blow-and-blow process, a mechanical transfer of the formed parison occurs, moving it from the blank mold to an adjacent blow mold where reheating and final forming of the parison to the desired container shape, consistent with the blow mold cavity, occurs.
An inherent problem in the use of the blow-and-blow process is the continued formation of glass particulate debris in the area of the neck ring. Such debris becomes entrained in the air flow and may become embedded in the parison or form a buildup in the air flow channel of the plunger mechanism. Another inherent problem in the blow-and-blow process, particularly in the production of narrow neck containers, is the inability to consistently produce glass containers free of settle wave and with uniform lightweight glass distribution in the container. This problem has usually been addressed in the industry by using equipment specifically designed to produce containers by a process known as "NNPB", or narrow neck press and blow.
Obtaining the speed, efficiency, and product consistency of the NNPB process through an improved blow-and-blow process has continued to be a goal which has until now eluded glass container manufacturers.